Our Oracle installation mysteriously stopped working. In particular, the Oracle Agent service would not start (OracleOraHome92Agent). The Windows Event Viewer was no help, it simply said "Agent service failed to launch the agent process." and "Faulting application agntsrvc.exe, version 0.0.0.0, faulting module unknown, version 0.0.0.0, fault address 0x00000000.". When I manually started the service from the services control panel, I got the additional helpful message "The handle is invalid".
I searched the Web for advice, but none of the suggestions were helpful. For example, one site suggested turning on tracing by adding the directive "dbsnmp.trace_level=admin" or "agentctl.trace_level=admin" to the file "${ORA_HOME}/network/admin/snmp_rw.ora", but those settings were not being respected. In fact, there was no evidence whatsoever in the Oracle directory that any processes were being started -- nothing in the log directory and nothing in the trace directory.
I used the SysInternals FILEMON utility to see what files were being accessed. It turns out that the service was attempting to launch a program from the C: drive even though Oracle was installed on the C: drive. This, in turn, was due to the fact that the Oracle registry entries had been overwritten with invalid values (due to an inappropriate .REG file being loaded).
All was well after I corrected the erroneous registry entries, pointing Oracle back to its true home directory.
